1. Field of the Invention
The present invention relates generally to a body frame for vehicles. More particularly, the invention relates to a body frame for a straddle-type vehicle with a saddle seat, which includes a head tube for steerably supporting a front suspension and a substantially rearwardly extending pipe member connected at the front end thereof to the head tube.
2. Description of Relevant Art
There are many known body frames for vehicles of a type with a saddle seat to be straddled by the driver (i.e., "straddle-type vehicles"), such as a motorcycle or a motorized tricycle, which include a head tube for steerably supporting a front suspension and a pipe member connected at the front end thereof to the head tube, the pipe member extending substantially rearwardly.
Most conventional body frames such as for motorcycles and motorized tricycles include a pipe frame which is constituted as a whole so as to extend substantially in the longitudinal direction of the vehicle and has fastened at the front end thereof a head tube adapted to steerably support a front suspension of the vehicle. As a typical example, a known body frame of the so-called cradle type includes a head tube forming the front end part thereof, a rearwardly extending main tube fastened at the front end thereof to the upper part of the head tube, a rearwardly and downwardly extending down tube fastened at the upper end thereof to the lower part of the head tube, a bottom frame rearwardly extending from the lower end of the down tube, and a rear frame extending upwardly from the rear end of the bottom frame and being connected to the rear end of the main tube, and in which an engine is mounted on the bottom frame.
Such a body frame for vehicles is normally subjected, particularly in the vicinity of a head tube thereof, to relatively high loads such as due to impacts from the road, through a front fork while the vehicle is travelling. For such reasons, there are employed a number of reinforcement members such as gussets for reinforcing fastened points and the like between the head tube and a down tube as well as between the head tube and a main tube. However, the head tube, which is adapted to suspend a front wheel through the front fork, requires high accuracy in the positioning thereof and, because of its being subjected to high loads, requires a sufficient joint strength to be provided for the welding. Thus, difficult and troublesome fitting work is necessary for the provision of reinforcement members about the head tube. Further, the proportion in number of the required reinforcement members to the component parts of such a body frame for vehicles tends to give rise to a number of problems in the assembly process of the body frame.
The present invention effectively overcomes the foregoing shortcomings and disadvantages attendant a conventional body frame for vehicles.